Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual copa nacional tem o FC Barcelona?
 ###Tabelas: CREATE TABLE season_2:_1938_—_1939 (season_2:_1938_—_1939_id AUTO_INCREMENT PRIMARY KEY, Episode VARCHAR, Title VARCHAR, Writer(s) VARCHAR, Preservation VARCHAR, Original airdate VARCHAR) CREATE TABLE singles:_19_11_titles_8_runner-ups (singles:_19_11_titles_8_runner-ups_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Year INT, Championship VARCHAR, Surface VARCHAR, Opponent in the final VARCHAR, Score in the final VARCHAR) CREATE TABLE grand_slam_men's_doubles_finals:_20_16–4 (grand_slam_men's_doubles_finals:_20_16–4_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Year INT, Championship VARCHAR, Surface VARCHAR, Partner VARCHAR, Opponents VARCHAR, Score VARCHAR) CREATE TABLE third_and_fourth_tiers (third_and_fourth_tiers_id AUTO_INCREMENT PRIMARY KEY, Season VARCHAR, Club VARCHAR, National League VARCHAR, National Cup VARCHAR, European Cup VARCHAR) CREATE TABLE sheffield_united_career (sheffield_united_career_id AUTO_INCREMENT PRIMARY KEY, Division VARCHAR, League Apps (Sub) INT, League Goals INT, FA Cup Apps (Sub) VARCHAR, FA Cup Goals INT, FL Cup Apps (Sub) INT, FL Cup Goals INT, Other Apps INT, Other Goals INT, Total Apps (Sub) VARCHAR, Total Goals INT)  
SELECT National Cup FROM third_and_fourth_tiers WHERE Club = fc barcelona